X3D Distributed Interactive Simulation (DIS) Implementation and Run-Time

Discovery of New Entities using X3DOM Don McGregor, Byron Harder, Don Brutzman .

Modeling, Virtual Environments Simulation (MOVES) Institute

Naval Postgraduate School, Monterey California

Web3D 2015 Conference, Crete Greece

18 June 2015

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Topics

• Standards Approach for Networked Virtual Environments (NVEs)– X3D, JavaScript, X3DOM and WebGL– DIS, WebSockets and WebRTC– Geospatial and Modeling Conventions

• X3DOM source for X3D DIS component• Performance and Demonstration• Conclusions and Future Work

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Standards-Based Approach for Networked Virtual Environments (NVEs)

• Motivation: Web is the real NVE– Everything else is smaller

• Twenty five year challenge

• “Break out” time!

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X3D, HTML5 and JavaScript

Multiple technologies need to be aligned• X3D and Script node• HTML and scripts• Bridging event models between X3D, HTML• X3DOM implementation, X3D v4 strategy

– http://x3dom.org– http://web3d.org/standards

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IEEE Distributed Interactive Simulation (DIS) Protocol

Network protocol, IEEE standard since 1995– IEEE 1278 is a communications standard for

physically based distributed simulations– Standard defines binary layout of messages

used to transmit simulation information– Often used in military applications since IEEE

1278 covers a wide range of data: entity location, velocity, and orientation, and more features such as signal and supply support

– Civilian applications: air-traffic control, etc.

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DIS protocol and X3D

– IEEE Distributed Interactive Simulation (DIS) protocol has been used for many years to build networked simulations that share state

– X3D DIS component aligns these capabilities with X3D scenes to enable sharing of state data

– EspduTransform: protocol data units (PDUs) for EntityState, Collision, Fire, Detonation

– Signals: ReceiverPdu,SignalPdu,TransmitterPdu– Real-time discovery, display of new entities:

DISEntityManager, DISEntityTypeMapping– Tutorial slides X3D for Advanced Modeling, DIS

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WebSockets Networking

• IETF/W3C standard API – RFC 6455 et al. (Wikipedia)– Language agnostic, includes JavaScript API

• Technical summary: – TCP-like sockets for web browsers, http/https– Reliable connection-oriented, provides framing– Client-server architecture (not peer-peer)– No broadcast or multicast

• Browser support excellent (including mobile)

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WebSockets diagram

A TCP socket is establishedfrom the web browser to the server, and stateupdates relayed throughthe server

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WebSockets Browser Adoption

~85% of deployed browser user base can use WebSockets, including mobile

http://caniuse.com/#feat=websockets

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WebRTC Networking

• IETF/W3C standard API– RFC standards still in development– Language agnostic with JavaScript API

• Browser support growing (including mobile)• Technical summary:

– UDP-like sockets for web browsers; encrypted– Best effort (e.g. “unreliable”) message-oriented,

acceptable to drop packets– Client-server or peer-peer (rendezvous point) – No broadcast or multicast

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WebRTC diagram

After signaling step, direct browser-to-browser communication of data possible using WebRTC UDP

Initial signaling step usingexternal rendezvous serviceallows browsers to find each other

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WebRTC Browser Adoption

~ 50% of installed browser user base is capable of using WebRTC

http://caniuse.com/#search=WebRTC

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Geospatial Conventions

• X3D: WGS84 and other datums allowed• Many different terrain models in the heterogeneous

DIS application domain• Caveat tester: current prototype uses “flat earth”

coordinates, clamped data inputs to surface

• DIS Coordinate System• Uses WGS84 Geocentric

coordinate system (only)• Problem: missing geospatial

conventions

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Modeling Conventions

• DIS– Orientation: Euler angle rotations from

geocentric earth fixed world coordinate system to body coordinate system

• X3D– Orientation convention: X nose, Y up, Z RHS– X3D Scene Authoring Hints collects numerous

“best practices” for compatible, scalable models– Savage Developers Guide lists our design

patterns for configuration and setup

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Performance

• Chen-Fu Hsiao thesis 2014 looked at WebSocket & WebRTC performance in a 3D environment– Significant performance differences between browsers at the time

of publication; this is likely to converge as implementations mature

• Approximately 5000 messages per second can be achieved with commodity desktop/laptop; low value of ~2000 messages per second with some implementations of WebRTC, likely due to immature browser implementation. Some test results > 10K PDUs/second !!

• That is a LOT of state transfer possible! – Enough for numerous networked games and NVES

• Further scalability possible through server-to-server bridging and filtering, area of interest management, etc.

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Demonstrations available

Web-Enabled DIS Maps with Websockets• https://track.nps.edu

• Simple text HTML• GoogleMaps API• Three.js• X3DOM

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Google Maps Demo

• Generate simulated traffic for San Francisco Bay Area

• Entities displayed on map real-time

• Can easily hook up live ship position feeds from Automated Information System (AIS) streams

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X3DOM

• Same traffic as Google Maps scene

• Live 3D entities added to scene

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Demonstration topology

• track.nps.edu• Backend: open-source Jetty WebSockets

Server, modified X3DOM javascript engine, models, and maps loaded from server

Crete Internet(proxies OK!)

NPS and otherenterprise firewalls

https://track.nps.eduServes content

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Various implementation issues

• Choosing and implementing a terrain model• Nonconventional entity models (and workarounds)• Modeling dynamic features like shot animation and

damage/destruction• Practical limits of unicast routing• EspduTransform + Transform workaround• Ungraceful degradation of connection-oriented

protocol (WebSocket) forwarding UDP stream– Application gateway filtering may be appropriate, TBD

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X3DOM source for X3D DIS component

• sourceforge.net/projects/open-dis – Java, JavaScript, C++, C#, Objective-C– XML definitions + code generators = agile, easy

• x3dom.org – Checked out a pull, sent back a push– github.com/mcgredonps/x3dom – Several work-weeks effort– Ready to work with Fraunhofer team

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X3D specification coverage

• Available for X3DOM– EspduTransform including ESPDU, Fire,

Detonation PDUs

• TODO– Collision PDU (integrated with EspduTransform)– Receiver, Signal, Transmitter PDU– Align X3D DIS and Geospatial components– Specify parameters for WebSockets, WebRTC

as part of url field

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Current State

• Connect to websocket server and load X3DOM-powered viewer page

• Display, navigate on flat map• Forward DIS via websocket• Display and move entities

driven by DIS PDUs• Display basic entity info

Demonstration video: https://savage.nps.edu/videos/McGregorHarderBrutzmanOpenDisX3domWeb3d2015.mov

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Remaining Issues

• Clamping entity elevation to (flat) sea level, need integration with geospatial X3D terrain

• Proper scaling while also maintaining useful user visibility and interaction conventions– “Highlighting bubble” for quick visual location

• Smooth animation between movement locations based on ESPDU dead reckoning

• Display FirePDUs, DetonatePDUs – boom!• Testing (and debugging) on bigger networks

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Conclusions

• X3DOM-based client deployment of DIS is feasible with initial implementation available– Availability of models, documentation, code

• Ready to make this technology mashup reliable and maintainable– Extending to entity control and PDU injection in

dynamic simulations

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Future work 1

• Integrate with X3DOM– Add, integrate other PDUs in EspduTransform– True dead reckoning

• Candidate future PDUs for X3D specification – Comment and Simulation Management PDUs– Intercom PDUs (Voice over IP)

• Open-DIS– Coordinate system conversion

libraries– Orientation conversion

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Future work 2

• X3D-Edit– Embed Jetty web-socket server– Auto-configure connections to Web3D channels– Simplified DIS network integration into scenes

• Web3D Projects Wish List– Stand-alone fully configured X3D server – Compatible with open-source GeoServer

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Contact

Don McGregor, Byron Harder, Don Brutzmanmcgredo@nps.edu brharder1@nps.edu brutzman@nps.edu

Modeling, Virtual Environments Simulation (MOVES) Institute

Naval Postgraduate School

Monterey California 93943-5000 USA

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BACKUP SLIDES

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Overview

• Use Cases• Sequence Diagram• Domain Model• Deployment Diagram• Current State• Remaining Issues• Conclusion

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X3D Simulation Viewing System

Simulation Observer

View Simulation inReal Time

Simulation FederationRecord Simulation

Run

PlaybackSimulation Run

Use Case Diagram

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WebsocketServerclientBrowser SecuritySystem

webpageConnection

requestConnection

dispatchAccessRequest

challengeSecurityCredentials

respondSecurityChallenge

approveSecuritySession

provideAvailableSimulations

spawn

connectToSimulation

sendSimulationSessionRules

sendInitialScene

entityModelRepository

requestEntityModels

sendEntityModels

Sequence Diagram: Session Setup

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WebsocketServerClientBrowser

X3Dscene

-location

SimulationX3Dmessage

+receiveFromSimulation()+sendToClient()

WebpageConnection

SimulationNetwork

-allowedCameraAngles-fogOfWar?-displaySelf?

SimulationSessionRules

-elevationData-textureData-levelOfDetail

TerrainData

-location

SimulationNativeMessage

< Connects-to

Spawns Communicates-with

1

*

Sets

< Conforms-to

Sends < ReceivesListens-to

^Broadcasts

-locationBounds

TerrainDataRepository

< Serves

Requests-from

Displays

-locationBounds

SimulationFederation

^Broadcasts-on

Domain Model

EntityModel-enumerationMapping

EntityModelRepository< Serves

Requests-from

Displays

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Internet

Client Browser

Websocket X3D Gateway Server

Deployment Diagram

Simulation Network

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Browser

Server Pages

X3DOM

X3DOM-DIS

X3DOM-DIS-PLUS

WebGL

X3D

HTML

Javascript

SimulationViewer

DIS

X3Dmodels__X3Dmodels_X3Dmodels

Package Dependencies